function prototype

Hi

The following function declaration doesn't work. It takes object flowfield and returns object matrix_square.

Code:

matrix_square eigenvalue(flow_field, flow_field);


matrix_square eigenvalue_plus(flow_field &ob, flow_field &ob1)
{

  int i;
  matrix_square temp;

    for (i = 0; i < Grids; i++)
      temp.ptr[i] = ob.ptr[i];							//Element 11
    for (i = 4*Grids; i < 5*Grids; i++)
      temp.ptr[i] = ob.ptr[i - 4*Grids] + ob1.ptr[i - 4*Grids];		//Element 22
    for (i = 8*Grids; i < 9*Grids; i++)
      temp.ptr[i] = 0;								//Element 33

return temp;
}

It's usually easiest to copy and paste in order to avoid issues like this.

Code:

matrix_square eigenvalue(flow_field &, flow_field &);

?

Leaving the parameter name in there costs you nothing.

I get the following error when I declare:

Code:

matrix_square eigenvalue(flow_field &, flow_field &);


matrix_square eigenvalue(flow_field &ob, flow_field &ob1)
{

  int i;
  matrix_square temp;

    for (i = 0; i < Grids; i++)
      temp.ptr[i] = ob.ptr[i];							//Element 11
    for (i = 4*Grids; i < 5*Grids; i++)
      temp.ptr[i] = ob.ptr[i - 4*Grids] + ob1.ptr[i - 4*Grids];		//Element 22
    for (i = 8*Grids; i < 9*Grids; i++)
      temp.ptr[i] = ob.ptr[i - 8*Grids] - ob1.ptr[i - 8*Grids];		//Element 33

return temp;
}

matrix_functions.C:110: error: ‘matrix_square’ does not name a type

Note the declaration is from a header file while the code itself is stored in a .C file

Make sure that matrix_square is declared before your function prototype, usually by including it's headerfile.

When I compile I type:

g++ -o supersonic_ob supersonic_ob.C matrix_functions.C -lm

supersonic_ob.C

Code:

//Declare header files

#include "matrix_square.H"  //Class definition
#include "matrix_functions.H"  //Function prototype

int main(){

flow_field ob, ob1;
matrix_square b;

b = eigenvalue_minus(ob, ob1);

}

matrix_function.C

Code:

matrix_square eigenvalue_minus(flow_field &ob, flow_field &ob1)
{

  int i;
  matrix_square temp;

    for (i = 0; i < Grids; i++)
      temp.ptr[i] = 0;								//Element 11
    for (i = 4*Grids; i < 5*Grids; i++)
      temp.ptr[i] = 0;								//Element 22
    for (i = 8*Grids; i < 9*Grids; i++)
      temp.ptr[i] = ob.ptr[i - 8*Grids] - ob1.ptr[i - 8*Grids];		//Element 33

return temp;
}

matrix_function.H

Code:

matrix_square eigenvalue_minus(flow_field &, flow_field &);

Hope I am clear enough.

All headers that are part of the translation unit are relevant and should be posted for any real analysis: can you also post "matrix_square.H"?

Here's matrix_square.H

Code:

class matrix_square { 

public:

  int i;
  double *ptr;

  matrix_square(){

    ptr = new double[square_points];
    assert( ptr!= 0);

 for(i = 0; i < square_points; i++)

	ptr[i] = 0;}

//copy constructor
matrix_square(const matrix_square &a){

  int i;
  ptr = new double[square_points];

  for(i = 0; i < square_points; i++)

    ptr[i] = a.ptr[i];

}

  ~matrix_square(){

    delete [] ptr;
}
};

Does matrix_function.C #include "matrix_square.H"? It should, because it uses a matrix_square. (It should also #include "matrix_functions.H".)

Each .C file should #include any .h files that contain declarations it needs.

Thanks you guys, got it working.